Methods for operating a steering wheel device with a combined heating and detection unit and heating and detection units

Abstract

The invention relates to two method for operating a steering wheel device (2) with a combined heating and detection unit (3), which has at least two electrodes (10, 11). In the first method, the electrodes (10, 11) are actuated alternately in a heating mode (14) and in a first detection mode (15) for detecting the presence of a hand (7), in which a first measured value is detected (S1) jointly for the electrodes (10, 11) and it is checked (S2) whether the detected first measured value deviates from a reference value, wherein only if this is the case are the electrodes (10, 11) controlled (S3) in a second detection mode (16), in which a respective second measured value is detected and analysed individually for each of the electrodes (10, 11). In the second method, a measurement is carried out between two electrodes (10, 11) to detect presence, wherein in this measurement a first electrode (10) of the two electrodes (10, 11) is controlled to heat the steering wheel device (2).

Description

[0001] Method for operating a steering wheel device with a combined heating and detection device and heating and detection devices

[0002] The invention relates to two methods for operating a steering wheel device with a combined heating and detection device. Furthermore, the invention relates to two combined heating and detection devices for a steering wheel device for a motor vehicle, a steering wheel device with a combined heating and detection device, and a motor vehicle with a steering wheel device.

[0003] A motor vehicle may have a steering wheel device in which a detection device is integrated. The detection device is designed to determine whether a user of the motor vehicle is currently touching the steering wheel device with at least part of a hand or is grasping it with at least one hand. The detection device can thus provide a hand recognition function, which can alternatively be referred to as hands-on detection (HOD).A check to determine whether the user is touching the steering wheel device with at least part of their hand or at least gripping the steering wheel device with their hand can be performed, for example, to determine whether the user is ready to resume manual steering of the motor vehicle if the steering of the motor vehicle is currently being performed by an at least partially automatic, in particular fully automatic, function, for example, a driver assistance system. The user is therefore preferably a driver of the motor vehicle.

[0004] The detection device can be designed as a capacitive detection device. It typically comprises a capacitive sensor. The capacitive sensor comprises at least one electrode and preferably several electrodes. The at least one electrode can be designed, for example, as a mat arranged around a steering wheel frame of the steering wheel device.

[0005] By means of the mat and thus by means of the electrode or electrodes, a heating function for the steering wheel can also be implemented, for example. The heating function can, for example, specify and implement an increase in the temperature of the steering wheel to a predetermined target temperature. The detection device can therefore actually be a combined heating and detection device. Typically, such a combined heating and detection device has various operating modes in which it is operated alternately. For example, it can be controlled alternately for a first time window in a heating mode to heat the steering wheel device and for a second time window in a detection mode to detect the presence of at least part of the hand in a gripping area of ​​the steering wheel device. However, in the case of multiple electrodes, all of which must be measured, this leads to relatively long interruptions in heating during the detection mode.It can therefore be energy-intensive to heat the steering wheel device to a predetermined target temperature and maintain it there, for example. The combined heating and detection system is therefore not very efficient.

[0006] It is the object of the invention to provide a solution by means of which both the detection of the presence of a hand in a gripping area of ​​a steering wheel device and its heating can be carried out efficiently.

[0007] The problem is solved by the subject matter of the independent patent claims.

[0008] A first aspect of the invention relates to a method for operating a steering wheel device with a combined heating and detection device. The steering wheel device can alternatively be referred to as a steering wheel. The steering wheel device is intended for a motor vehicle. In particular, it is installed in the motor vehicle. This method can be referred to as the first method.

[0009] The heating and detection device has at least two electrodes that are distributed over a steering wheel rim of the steering wheel device. The respective electrode can be designed as a mat, in particular as a sensor mat. For example, a first electrode of the at least two electrodes can be arranged in at least a partial area of ​​an inner side of the steering wheel device that faces a steering wheel hub of the steering wheel device. A second electrode of the at least two electrodes can be arranged on at least a partial area of ​​an outer side of the steering wheel device that is opposite the inner side. This makes it clear that electrodes can, for example, be arranged opposite one another, for example with respect to a steering wheel skeleton of the steering wheel device.Alternatively or additionally, one of the electrodes can be arranged at least on a partial area of ​​an underside of the steering wheel device that faces a steering column of the steering wheel device, and / or on at least a partial area of ​​an upper side of the steering wheel device that is opposite the underside and faces a driver's seat of the motor vehicle when the steering wheel device is installed in a designated installation position in the motor vehicle.

[0010] The at least two electrodes are alternately controlled in a heating mode for heating the steering wheel device and in a first detection mode for detecting the presence of at least part of a hand in a gripping area of ​​the steering wheel device. For example, the electrodes can be operated in heating mode for a first time window of, for example, 8 milliseconds and then in the first detection mode for a second time window of, for example, 2 milliseconds. Alternatively, the two time windows can be of equal length. Time windows other than those mentioned are possible. To set the respective mode, a switch of the heating and detection device can be provided, by means of which it is possible to switch between the modes.

[0011] It is provided that in the first detection mode a first measured value is recorded jointly for the at least two electrodes. The first measured value depends, for example, on whether at least part of the hand is present in the gripping area or not. The first measured value also varies, for example, depending on whether only individual fingers of the hand are touching the steering wheel rim or whether the hand is gripping the steering wheel rim. Furthermore, the first measured value is influenced, for example, by whether a single hand or two hands are present in the gripping area. The gripping area is, for example, a surface of the steering wheel device that is arranged in the detection area of ​​at least one of the plurality of electrodes of the heating and detection device. The first measured value is recorded jointly for all electrodes, i.e. at least for the two electrodes. This means that it is recorded for the electrodes simultaneously.For example, measurements are performed in parallel for all electrodes, with exactly one single value being determined that describes all these measurements taken together. This single value is the first measured value. In the first detection mode, for example, the at least two electrodes are operated in parallel with the same potential.

[0012] A check is carried out to determine whether the recorded first measured value deviates from a predefined reference value. Only if this is the case are at least two electrodes activated in a second detection mode to detect the presence of at least part of the hand in the gripping range of the steering wheel device. The reference value can, for example, be predefined as a function of an activated driver assistance system. It can therefore, for example, be selected such that the deviation from the reference value is used to detect whether the steering wheel rim is being gripped with both hands or whether no part of the hand is present in the gripping range. The reference value can therefore be selected accordingly, depending on whether or not touching and / or gripping the steering wheel rim is currently required. The first measured value deviates from the predefined reference value if it is greater or smaller than this.Alternatively or additionally, a reference value range can be specified, i.e., an interval of several reference values. If the first measured value lies outside the specified reference value range, the system switches to the second detection mode.

[0013] If the first measured value does not deviate from the specified reference value, i.e., if it matches it, or if it is within the specified reference value range, the heating and detection device switches back to heating mode. The alternating control in heating mode and the first detection mode continues. In this case, no switch to the second detection mode occurs.

[0014] In the second detection mode, a second measured value is recorded and evaluated individually for each of the at least two electrodes. For example, self measurements are carried out for each of the at least two electrodes in the second detection mode. With exactly two electrodes, the second measured value for the first electrode is recorded first, followed by the second measured value for the second electrode, or vice versa. However, this takes more time than the joint measurement in the first detection mode. This extends the time interval between two heating phases, which at least makes heating efficient. Alternatively, or in addition to the self measurement, mutual measurements can be carried out with more than two electrodes, in which at least two electrodes are always measured against each other.These joint measurements also allow a second measurement value to be determined for each of the electrodes.

[0015] The respective second measured value is also evaluated. The evaluation includes, for example, comparing each of the second measured values ​​with a further reference value and / or a further reference value range. For example, as a result of the measurements in the second detection mode, it is determined whether the presence or absence of the hand in the gripping area, as specified by the reference value or the reference value range, can also be detected in the individual measurements at the electrodes, i.e., can be determined or not. Detailed measurements of the individual electrodes therefore only take place if the previously carried out joint measurement revealed an abnormality. This makes the detection function of the heating and detection device efficient. Overall, both the detection of the presence of the hand in the gripping area of ​​the steering wheel device and its heating are carried out efficiently.

[0016] Further advantages are that, at least in the first detection mode, the influence of crosstalk on the measurement is reduced. This is due at least to the fact that the at least two electrodes are operated in parallel with the same potential when measured together. Furthermore, the reference value or the reference value range can also include the influence. Furthermore, shielding of the electrodes and / or electronics of the steering wheel device, i.e. a so-called SHIELD signal, can be improved because the electrodes are operated in parallel with the same potential in the first detection mode. This results in a homogeneous charge of the electrodes. This improves the measurement of a change in capacitance when at least part of the hand is present in the gripping area.

[0017] One embodiment provides that by respectively evaluating the respective recorded second measured value, the electrode of the at least two electrodes is determined in whose detection range at least part of the hand is present. During the individual measurements in the second detection mode, it can thus be determined in which part of the steering wheel rim the hand is located and in which it is not. This is particularly useful with more than two electrodes that are distributed around the steering wheel rim and divide it into several zones. The presence or absence of at least part of the hand can then be individually detected and provided for each zone. Furthermore, based on the respective measured value, it can be differentiated whether individual fingers or the entire hand are present in the gripping area. Known methods for evaluating measured values ​​from a detection device of a steering wheel device can be used here.

[0018] In addition, one embodiment provides that the at least two electrodes are controlled in heating mode again after being controlled in the second detection mode. After each of the electrodes has been measured individually, the mode changes back to heating mode. Subsequently, for example, the first detection mode can be provided again. The heating and detection device therefore always attempts to switch alternately between heating mode and the first detection mode, provided the first measured value permits. However, if a switch to the second detection mode is necessary, a return to heating mode and alternating operation in heating mode and first detection mode is made as soon as possible. This contributes to ensuring that both the detection of the presence of the hand in the gripping area of ​​the steering wheel device and its heating are always carried out efficiently.

[0019] A further aspect of the invention relates to a method for operating a steering wheel device with a combined heating and detection device, which has at least two electrodes arranged distributed over a steering wheel rim of the steering wheel device. The steering wheel device corresponds, for example, to the steering wheel device described above in terms of the arrangement and design of the electrodes. In a measuring mode, a measurement is performed between two of the at least two electrodes in order to detect the presence of at least part of a hand in a gripping area of ​​the steering wheel device. This method can be referred to as the second method.

[0020] The heating and detection device is therefore designed to perform a measurement between two of the at least two and thus multiple electrodes in order to detect or determine the presence of the hand. By evaluating measurement information determined during the measurement between the two electrodes, the presence of the hand or the absence of the hand in the gripping area can be detected. For this purpose, the heating and detection device can have a measuring unit that records the measurement information. Therefore, no separate measurement of the respective electrode is performed, but rather the joint measurement using at least two electrodes mentioned above. This makes the detection of the presence of the hand in the gripping area particularly reliable and precise compared to pure separate measurements. The measurement between the two electrodes can be understood as a coupling of the two electrodes.

[0021] The heating and detection device is preferably operated with an alternating voltage, so that the steering wheel device can have an alternating voltage source for the heating and detection device, or the steering wheel device can be supplied with power by means of an alternating voltage source external to the steering wheel, which can be a component of the motor vehicle. The measurement information can therefore describe an impedance, in particular a capacitive component of the impedance, wherein the heating and detection device exhibits the impedance when it is supplied with alternating current. This operation with alternating voltage can also be provided in the first aspect of the invention.

[0022] During the measurement between the two electrodes, a first of the two electrodes is controlled to heat the steering wheel device. Thus, heating and detection of the presence of at least part of the hand within the gripping area of ​​the steering wheel device occur simultaneously. The measurement mode or detection mode of the heating and detection device is thus combined with the heating mode of the heating and detection device. A second of the two electrodes is not controlled to heat, but serves only to detect the presence of the hand.

[0023] The detection of the presence of the hand and thus the measurement between the two electrodes occurs particularly at the beginning and / or end of the heating process. It thus occurs during a phase of switching the first electrode on and / or off as the heating electrode. During this phase, a voltage applied to the first electrode is, for example, increased or decreased.

[0024] This makes it possible for both the detection of the presence of the hand in the gripping area of ​​the steering wheel device and its heating to be carried out efficiently, since these two tasks of the heating and detection device are carried out simultaneously and thus not necessarily one after the other.

[0025] According to one embodiment, it is provided that, as a measurement between the two electrodes, the first electrode is operated in an excitation mode in which a temporal variation of an electrical charge of the first electrode is predetermined. The first electrode is consequently excited or stimulated in the excitation mode. It can therefore alternatively be referred to as the transmitting electrode. The charge of the first electrode is therefore not constant in the excitation mode, so that, for example, a temporally varying electromagnetic field is generated in the heating and detection device. The second electrode of the two electrodes is simultaneously operated in a receiving mode in which capacitive measurement information describing the second electrode can be detected. The second electrode can therefore be referred to as the receiving electrode. The capacitive measurement information is, for example, a capacitance, in particular a capacitive component of the impedance.The acquired measurement information is influenced by the stimulated first electrode, i.e., by the generated time-varying electromagnetic field. Since at least the first electrode influences the second electrode, a measurement is performed between at least these two electrodes, thus forming a joint measurement.

[0026] The recorded capacitive measurement information is influenced at least by the temporal variation of the electrical charge of the first electrode, so that the presence of at least part of the hand is detectable, i.e., can be recognized, by evaluating the recorded capacitive measurement information. It is therefore provided that the first electrode stimulates the second electrode by changing its charge. It is assumed that the two electrodes are arranged in such a way that the electromagnetic field generated by the change in charge affects the capacitive measurement information recorded by the second electrode and thus affects the second electrode. Taking into account the predetermined temporal variation in the charge, it is possible to estimate at least which capacitive measurement information is expected for the second electrode, i.e., which capacitive measurement information is stimulated.If the hand now moves into the gripping range of the steering wheel, this affects the capacitive measurement information recorded for the second electrode. This effect can be determined by evaluating the measurement information. This illustrates how the presence of the hand can be detected and thus determined.

[0027] The first electrode used for heating is in excitation mode due to the voltage applied to it for heating. Using the second electrode in receive mode, in addition to heating, the presence of at least part of the hand is detected, so that the heating and detection functions occur simultaneously. Heating occurs, for example, in an area or zone of the first electrode, and the hand is detected in the area or zone of the second electrode.

[0028] In addition, one embodiment provides for the mode of the respective electrode to be continuously switched between the excitation mode and the reception mode, whereby only the respective electrode operated in the excitation mode is always controlled to heat the steering wheel device. With exactly two electrodes, for example, the first electrode is initially controlled for a first time window and then the second electrode is controlled for a second time window. After the second time window, the first electrode is again controlled for the first time window and so on. The two time windows can be selected to be of the same length or different lengths. It is therefore not intended that the first electrode is constantly operated in excitation mode and the second electrode in reception mode, but rather the two electrodes repeatedly switch between the two possible modes.It is intended that, for example, the change between the modes occurs after an interval in the range of milliseconds, for example between 100 and 300 milliseconds. If, for example, the hand grasps the steering wheel, it is typically within the detection range of two electrodes arranged around the steering wheel rim. The presence of the hand is therefore detected for, for example, the electrode that is currently in receive mode. This can be used to detect, for example, a grip on the steering wheel rim or the steering wheel by alternately recording and evaluating the capacitive measurement information for the first and second electrodes, with the presence of the hand then being detected for both electrodes in receive mode.

[0029] Preferably, more than two electrodes are provided, in particular four electrodes. During or at a time offset from the operation of, for example, the first electrode for heating, the other three electrodes can each be operated at least temporarily in receive mode. At least partially simultaneously, for example, the second electrode can be controlled for heating, with, for example, a third and fourth electrode of the four electrodes now each being operated in receive mode. Thus, several sub-areas of the steering wheel rim can be heated simultaneously if the heating and detection device has more than two electrodes.

[0030] A preferred embodiment provides that the first electrode experiences a voltage change. For this purpose, the first electrode can first be switched off for a predetermined time interval and then switched on. A voltage drop or voltage value is specified via the first electrode, for example when switched on, so that if at least part of the hand is present in the gripping area of ​​the steering wheel device during the voltage change, in particular when switched on, a measured value of the measurement between the two electrodes depends on the part of the steering wheel rim in which at least part of the hand is present. By evaluating the measured value, the presence of at least part of the hand is detected in a spatially resolved manner. For example, it can be provided that connections for, for example, two electrodes run at a first location on the steering wheel rim. The voltage drop or voltage value is now measured at the connections for the first electrode.A voltage value is specified, meaning this electrode is controlled for heating and operated in excitation mode. For example, a high voltage can be applied to a first of the two terminals of this electrode compared to the voltage applied to a second of the two terminals. The voltage applied to the second terminal is, for example, 0 volts. In the area of ​​the first terminal, a maximum measurable value can be recorded when measuring between the two electrodes. However, in the area of ​​the second terminal, a minimum measurable value is recorded when measuring between the two electrodes.

[0031] If at least part of the hand is located at a second location on the steering wheel rim that is different from the first location, a measured value is recorded that lies between the maximum and the minimum measurable measured value. If the second location is opposite the first location, the measured value is, for example, 50 percent of the maximum measurable measured value. However, if the second location is, for example, midway between the first location and the opposite location, the measured value is 25 percent or 75 percent of the maximum measurable measured value, depending on whether this second location is further away from the first connection or closer to it than the opposite location. Using, for example, two electrodes, the location on the steering wheel rim at which the hand grips the steering wheel rim can be determined. This means that three or more partially overlapping electrodes are not necessary for this precise location recording.This leads to a simplification of the heating and detection device compared to other location-specific detection techniques.

[0032] Alternatively or in addition to switching the first electrode on and off, it can be provided that a different, comparatively smaller voltage change is specified at the first electrode. The greater this voltage change, the better the precise location detection can be achieved. Therefore, the voltage is preferably first reduced to zero by switching the first electrode off and then increased again to maximum by switching it on. However, smaller voltage changes without switching off and then on are possible. Such a voltage change can be specified, for example, by the control device of the steering wheel device.Furthermore, the voltage change can occur when the engine is started, when an energy-intensive driver assistance system of the motor vehicle is activated or deactivated, and / or when a vehicle battery of the motor vehicle is charged in recuperation mode. This voltage change can be used for the precise location detection of the hand's presence at the time of this voltage change. A noise phase in the voltage of the steering wheel's power supply can be used to perform the precise location detection. In these examples, it is assumed that the second electrode is operated in receive mode synchronously with the voltage change. The described method for the spatially resolved detection of the hand's presence can be transferred to any capacitive sensor design, based, for example, on capacitively sensed touches.It is suitable, for example, for a touch-sensitive switch where the movement of a finger across the switch needs to be detected and evaluated. A slide function can therefore be implemented. Using this switch, for example, the volume of an audio output in a vehicle and / or the temperature of a vehicle's air conditioning system can be adjusted by detecting the location of the touch on the switch and linking it to a predefined setting parameter for the audio output or air conditioning system.

[0033] An additional embodiment provides for the spatially resolved determination described above to be checked. For this purpose, a voltage change is applied to the first electrode again, for example by first switching it off for a predetermined time interval and then switching it on again. Particularly upon switching on, a reversed voltage drop, in particular a charge change in the opposite direction, is specified across the first electrode than before. For example, a higher voltage is now applied to the second terminal compared to the first terminal. This changes the proportions of the maximum measurable measured value that are expected at the individual locations on the steering wheel rim when the hand grasps the rim at those locations.The measured value is now evaluated again, but only if the same sub-area of ​​the steering wheel rim is determined in both evaluations is presence information describing this sub-area provided. For example, if 75 percent of the maximum measurable measured value was recorded before the check and thus a hand location midway between the first location and the opposite location was determined, it is expected that only 25 percent of the maximum measurable measured value will be recorded during the repeated evaluation. If this is the case, both measured values ​​point to the same location on the steering wheel rim. This location is then described by the presence information. The respective location is understood here as a sub-area of ​​the steering wheel rim because the hand that grips the steering wheel rim always covers a certain area (sub-area) and therefore more than one specific point (location).This ensures that the spatially resolved detection of the hand's presence has been reliably performed before the presence information is provided, for example, to a currently activated driver assistance system in the motor vehicle. In connection with the two described aspects of the invention, one exemplary embodiment provides that after the at least two electrodes have been activated in the second detection mode, the at least two electrodes are activated in the measuring mode. Following the second detection mode, in which no heating occurs but the individual electrodes are activated individually, the heating and detection device switches to the measuring mode, in which heating and the presence of the hand are detected simultaneously, with the joint measurement being performed for this purpose.It is now checked whether a result concerning the presence of at least part of the hand in the gripping area of ​​the steering wheel device, which was obtained in the second detection mode, corresponds to such a result in the measuring mode. Such a result in the measuring mode is a result concerning the presence of at least part of the hand in the gripping area of ​​the steering wheel device. The two described methods for operating the steering wheel device with the combined heating and detection device are therefore applied consecutively to ensure that no measurement error has occurred when applying the first or second of the two methods. The method with the measuring mode represents a verification level and a redundant method to the method with the detection modes.This is particularly suitable for driver assistance systems with safety requirements that require or require a redundant design of components and / or functions of the motor vehicle.

[0034] A further exemplary embodiment provides that if the presence of at least part of the hand in the gripping range of the steering wheel device was detected when the at least two electrodes were activated in the measuring mode, the at least two electrodes are subsequently activated in the first detection mode and / or in the second detection mode. A check is then carried out to determine whether the presence of at least part of the hand in the gripping range of the steering wheel device is also detected by means of the first or second detection mode. In other words, the heating and detection device is initially operated according to the second method, which provides the measuring mode in which heating and the presence of the hand are detected simultaneously, with the joint measurement being carried out for this purpose. If the presence of the hand is detected here, this result is checked, for which the first method is applied.This can initially be operated alternately in heating mode and the first detection mode. If a deviation from the reference value is detected, the system can switch to the second detection mode. Alternatively, the system can switch directly to the second detection mode after the measurement mode. It can be provided that no switch to heating mode occurs between the measurement mode and the first detection mode. It can be checked whether a result regarding the presence of at least part of the hand in the gripping area of ​​the steering wheel device, which was obtained in the measurement mode, corresponds to a similar result in the first and / or second detection mode.

[0035] The two described methods for operating the steering wheel device with the combined heating and detection device are therefore applied sequentially to ensure that no measurement error has occurred when applying the second of the two methods. The method with the detection modes represents a verification level and a redundant method to the method with the measurement mode. This is particularly suitable for driver assistance systems with safety requirements that require or require a redundant design of components and / or functions of the motor vehicle.

[0036] In the exemplary embodiments for testing the respective method, the trigger can be specified as detecting or determining the absence of the hand instead of detecting or recognizing the presence of at least part of the hand within the gripping area of ​​the steering wheel device. The trigger depends, for example, on the activated driver assistance system.

[0037] An additional exemplary embodiment provides that only if a match was determined during the check is result information describing the presence or absence of at least part of the hand in the gripping area of ​​the steering wheel device detected and provided, in particular by means of a control device of the steering wheel device. It can therefore be provided that the result of one of the two methods alone is not sufficient for further use. This leads to consistently reliable detection of the presence of at least part of the hand, in particular the entire hand, in the gripping area, since this presence is only provided as result information, for example, for the activated driver assistance system, upon two detections.

[0038] Advantages of the described methods include, for example: a reduction in the effects of cross-talk between the electrodes when detecting the presence of the hand; cross-talk can be exploited to detect moisture in the steering wheel device by taking into account the increase in coupling due to the impedance between the electrodes; improvement of the heating performance either by optimising the detection mode measurement periods and / or by using the measurement mode measurement periods; optimization of the quiescent current, since the time for the hand presence measurement is shorter when the first detection mode is activated; reduction of the load on the SHIELD signals; and / or improvement of electromagnetic interference (EMI performance), for example by reducing radiated noise (RF noise), since in the first detection mode all electrodes are measured simultaneously.

[0039] A further aspect of the invention relates to a combined heating and detection device for a steering wheel device for a motor vehicle, wherein the heating and detection device has at least two electrodes and is designed to control the at least two electrodes alternately in a heating mode for heating the steering wheel device and in a first detection mode for detecting a presence of at least part of a hand in a gripping area of ​​the steering wheel device.The heating and detection device is designed to jointly detect a first measured value for the at least two electrodes in the first detection mode, to check whether the detected first measured value deviates from a predetermined reference value, and only if this is the case, to control the at least two electrodes in a second detection mode to detect the presence of at least part of the hand in the gripping area of ​​the steering wheel device, in which a respective second measured value is individually detected and evaluated for each of the at least two electrodes. At least the exemplary embodiments described for the first method apply analogously to this heating and detection device.

[0040] A further aspect of the invention relates to a combined heating and detection device for a steering wheel device for a motor vehicle, wherein the heating and detection device has at least two electrodes and is designed to perform a measurement between two of the at least two electrodes in a measuring mode in order to detect the presence of at least part of a hand in a gripping area of ​​the steering wheel device. The heating and detection device is designed to control a first of the two electrodes during this measurement to heat the steering wheel device. At least the exemplary embodiments described for the second method apply analogously to this heating and detection device. An additional aspect of the invention relates to a steering wheel device for a motor vehicle with a combined heating and detection device as described above.The at least two electrodes of the heating and detection device are arranged distributed on a steering wheel rim of the steering wheel device.

[0041] One aspect of the invention relates to a motor vehicle with a steering wheel device as described above. The motor vehicle is, for example, a passenger car, a truck, a bus, a motorcycle, and / or a moped. The motor vehicle can have the described control device.

[0042] A further aspect of the invention relates to a control device for the steering wheel device and / or the heating and detection device. The control device is designed to carry out the respective described method. The control device carries out the respective described method, in particular an exemplary embodiment or a combination of exemplary embodiments of the respective described method. The control device has a processor device. The processor device can have at least one microprocessor and / or at least one microcontroller and / or at least one FPGA (Field Programmable Gate Array) and / or at least one DSP (Digital Signal Processor). Furthermore, the processor device can have program code, which can alternatively be referred to as a computer program product. The program code can be stored in a data memory of the processor device.

[0043] A further aspect of the invention relates to a computer program product. The computer program product is a computer program. The computer program product comprises instructions that, when the program is executed by a computer, such as by the control devices, cause the computer to perform the corresponding steps of the respective described method.

[0044] The exemplary embodiments described in connection with the respective method according to the invention, individually and in combination with one another, apply accordingly, as applicable, to the respective heating and detection device according to the invention, the steering wheel device according to the invention, the motor vehicle according to the invention, the control device according to the invention, and the computer program product according to the invention. The invention encompasses combinations of the described exemplary embodiments.

[0045] Detecting the presence of the hand or at least part of the hand can alternatively be referred to as determining, determining, or ascertaining the presence within the meaning of the invention. Detecting the presence of the hand can be understood here as detecting the presence of at least part of the hand, and vice versa.

[0046] Showing:

[0047] Fig. 1 is a schematic representation of a motor vehicle with a steering wheel device;

[0048] Fig. 2 is a schematic representation of a steering wheel device;

[0049] Fig. 3 is a schematic representation of a first method for operating a steering wheel device with a combined heating and detection device;

[0050] Fig. 4 is a schematic representation of switch positions for the method in Fig. 3;

[0051] Fig. 5 is a schematic representation of a second method for operating a steering wheel device with a combined heating and detection device;

[0052] Fig. 6 is a schematic representation of an embodiment of the method according to Fig. 5;

[0053] Fig. 7 shows a schematic representation of a signal flow graph of a method for the precise location detection of the presence of a hand in a gripping area of ​​a steering wheel device; and

[0054] Fig. 8 shows a schematic representation of a signal flow graph of a method for checking the methods according to Fig. 3 and Fig. 5 or Fig. 6. In the figures, functionally identical components are provided with the same reference numerals.

[0055] Fig. 1 shows a section of the interior of a motor vehicle 1. The motor vehicle 1 has a steering wheel device 2. The steering wheel device 2 has a heating and detection device 3, which is integrated into the steering wheel device 2 and is therefore a component of the steering wheel device 2, arranged below a surface of the steering wheel device 2. The steering wheel device 2 can alternatively be referred to as a steering wheel.

[0056] The steering wheel device 2 has a steering wheel rim 4 and a central steering wheel hub 9. An axis A runs perpendicular to the surface of the steering wheel device 2. The steering wheel rim 4 or the steering wheel device 2 has an inner side 5 facing the steering wheel hub 9. It also has an outer side 6 opposite the inner side 5 and thus facing away from the steering wheel hub 9. The outer side 6 faces the surroundings of the steering wheel device 2.

[0057] In Fig. 1, two hands 7 of a user 8, in particular a driver of the motor vehicle 1, grasp the steering wheel device 2, wherein they encompass the steering wheel rim 4 in two different partial areas of the steering wheel rim 4.

[0058] Fig. 2 shows the steering wheel device 2 with the combined heating and detection device 3. This device has at least two electrodes 10, 11, which are distributed over a steering wheel rim 4 of the steering wheel device 2. Here, exactly two electrodes 10, 11 are sketched as an example. A first electrode 10 of the two electrodes 10, 11 faces the inner side 5. A second electrode 11 of the two electrodes 10, 11 faces the outer side 6. The two electrodes 10, 11 are thus opposite one another. Alternatively or additionally, a respective electrode 10, 11 can be arranged on an underside of the steering wheel device 2, which faces a steering column of the steering wheel device 2, and / or on an upper side of the steering wheel device 2 opposite the underside, which upper side faces the user 8. The respective electrode 10, 11 can face only a partial area of ​​the respective side.The steering wheel device 2 and / or the combined heating and detection device 3 has a control device 19. This comprises a switch unit 12, which can alternatively be referred to as a switch or decoupling module. The switch unit 12 is designed to specify a mode for the respective electrode 10, 11. For this purpose, two connections 13 are provided for each of the electrodes 10, 11, which connect the switch unit 12 to a beginning and an end of the respective electrode 10, 11. Therefore, four connecting cables are shown here.

[0059] The mode of the respective electrode 10, 11 can be, for example, a heating mode 14, a first detection mode 15, a second detection mode 16, and / or a measuring mode 17. For the first detection mode 15, the second detection mode 16, and / or the measuring mode 17, the control device 19 can have a microcontroller 18. This can be referred to as an MCU.

[0060] Fig. 3 illustrates a first method for operating the steering wheel device 2 with the combined heating and detection device 3. The at least two electrodes 10, 11 are controlled alternately in heating mode 14 for heating the steering wheel device 2 and in the first detection mode 15 for detecting the presence of at least part of the hand 7 in a gripping area of ​​the steering wheel device 2. Here, a voltage U or a current I is plotted against time t. It is clear that in heating mode 14, a higher voltage U is applied or a higher current I flows than in the first detection mode 15. Furthermore, heating mode 14 lasts longer than the first detection mode 15.

[0061] In the first detection mode 15, a first measured value is recorded jointly for the at least two electrodes 10, 11. This occurs, for example, in a method step S1. A method step S2 then checks whether the recorded first measured value deviates from a predetermined reference value. This is determined here during the second activation in the first detection mode 15. A reference value deviation 20 therefore occurs. Only if this occurs, i.e. only if the recorded first measured value deviates from the predetermined reference value, are the at least two electrodes 10, 11 activated in a method step S3 in the second detection mode 16. The second detection mode 16 is designed to detect the presence of at least part of the hand 7 in the gripping area of ​​the steering wheel device 2. In the second detection mode 16, a respective second measured value is recorded and evaluated individually for each of the at least two electrodes 10, 11.Here, in the second detection mode 16, a single measurement is taken successively for the first electrode 10 and for the second electrode 11. By evaluating the respective second measured value acquired, the electrode 10, 11 of the at least two electrodes 10, 11 in whose detection range at least part of the hand 7 is present can be determined.

[0062] After being activated in the second detection mode 16, the at least two electrodes 10, 11 can be activated again in heating mode 14 in a method step S4. Subsequently, the mode changes back to the first detection mode 15, for example, and so on.

[0063] Fig. 4 illustrates the difference between the first detection mode 15 and the second detection mode 16. Here, individual switches 21 are shown for each of the two electrodes 10, 11, via which the respective electrode 10, 11 can be connected to or disconnected from an alternating current source 22 at its input and output. The alternating current source 22 is, for example, a component of the control device 19.

[0064] In the first detection mode 15, all individual switches 21 are closed, so that both electrodes 10, 11 are measured together. This results in the first measured value. The same potential is applied to both electrodes 10, 11. In the second detection mode 16, the individual switches 21 are open for one of the two electrodes 10, 11 and closed for the other. Thus, in the upper illustration, the second electrode 11 can be measured individually, and in the lower illustration, the first electrode 10. These two measurements each result in one of a total of two second measured values. In terms of time, the two measurements are carried out one after the other and thus separately from one another.

[0065] Fig. 5 illustrates a second method for operating the steering wheel device 2 with the combined heating and detection device 3. Here, the heating and detection device 3 is operated in measuring mode 17. In this mode, a measurement is taken between two electrodes 10, 11 of the at least two electrodes 10, 11 in order to detect the presence of at least part of a hand 7 in the gripping area of ​​the steering wheel device 2. During this measurement in measuring mode 17, the first electrode 10 of the two electrodes 10, 11 is controlled to heat the steering wheel device 2.

[0066] As a measurement between the two electrodes 10, 11, the first electrode 10 is operated in an excitation mode in which a temporal variation of an electrical charge of the first electrode 10 is predetermined. The second electrode 11 is simultaneously operated in a reception mode in which capacitive measurement information describing the second electrode 11 can be detected. The detected capacitive measurement information is influenced at least by the temporal variation of the electrical charge of the first electrode 10. By evaluating the detected capacitive measurement information, the presence of at least part of the hand 7 can be detected and thus determined.

[0067] A mode of the respective electrode 10, 11 can be continuously switched between the excitation mode and the reception mode, whereby only the respective electrode 10, 11 which is operated in the excitation mode is controlled to heat the steering wheel device 2.

[0068] Here, heating is initially achieved using the first electrode 10, which is operated in excitation mode. This electrode 10 is therefore symbolically assigned to heating mode 14. At the same time, the measurement information is recorded for the second electrode 11, which is operated in reception mode. This thus measures the presence or absence of the hand 7. It is therefore marked as measurement mode 17. The two electrodes 10, 11 then switch modes, so that the second electrode 11 now contributes to heating and the first electrode 10 contributes to detecting the hand 7, i.e., to recognizing the presence of the hand 7. Here, heating can be carried out continuously using one of the electrodes 10, 11. After that, the outlined temporal sequence is repeated, for example.

[0069] Fig. 6 schematically shows the second method with more than two electrodes 10, 11. Here, for example, a third electrode 23 and a fourth electrode 24 are provided. The steering wheel device 2 therefore has four electrodes 10, 11, 23, 24. More than four electrodes 10, 11, 23, 24 can also be provided. Here, for example, heating is carried out first with the third electrode 23 and a measurement is taken between this and the first electrode 10 in order to detect the presence of the hand 7. While the third electrode 23 is still heating, heating can already begin with the fourth electrode 24 and a measurement can be taken between this and the second electrode 11 in order to detect the presence of the hand 7. In addition, towards the end of the respective heating, a measurement can also be carried out with one of the other electrodes 10, 11, 23, 24 in receive mode in order to detect the presence of the hand 7.During heating with the third electrode 23, a measurement can also be taken together with the second electrode 11 or the fourth electrode 24 to detect the presence of the hand 7 when the excitation mode of the third electrode 23 is switched off. Since the duration of the respective measurement to detect the presence of the hand 7, which is again marked here as measurement mode 17, is shorter than the respective heating duration, which is marked here as heating mode 14, two measurements can therefore be taken during heating together with several electrodes 10, 11, 23, 24 in receive mode. Here, the steering wheel device 2 can be heated simultaneously in several sub-areas, since the individual heating phases can at least partially overlap in time.

[0070] In Fig. 5 and Fig. 6, the voltage U and the current I are plotted against time t. It is clear that a higher voltage U is applied for heating, or a higher current I flows, than for detecting the presence of hand 7. Furthermore, heating takes longer than detecting the presence of hand 7.

[0071] Fig. 7 shows further method steps for the second method. In a method step S5, the first electrode 10 is first switched off for a predetermined time interval and then switched on in a method step S6, wherein a voltage drop or voltage value is specified via the first electrode 10 upon switching on. If at least part of the hand 7 is present in the gripping area of ​​the steering wheel device 2 during switching on, a measured value of the measurement between the two electrodes 10, 11 depends on the partial area of ​​the steering wheel rim 4 in which at least part of the hand 7 is present. The presence of at least part of the hand 7 is now detected with spatial resolution by evaluating the measured value. Therefore, partial area information 25 can be determined which indicates the partial area of ​​the steering wheel rim 4 for which presence was detected.

[0072] It can now be checked whether the partial area information 25 is correct. For this purpose, in a method step S7, the first electrode 10 is first switched off again for a predetermined time interval and then switched on in a method step S8. When switched on, a reverse voltage drop, in particular a charge change in the opposite direction, is specified via the first electrode 10 than before, and the evaluation of the measured value is repeated. Therefore, another piece of partial area information 25' is determined here. It can now be checked in a method step S9 whether the same partial area was determined in both evaluations. The two pieces of partial area information 25, 25' are therefore compared with one another. Only if the same partial area of ​​the steering wheel rim 4 was determined in both evaluations is presence information 26 describing this partial area provided in a method step S10.The presence information 26 may correspond to the sub-area information 25, 25' or may contain additional information, for example an indication that the sub-area was determined twice.

[0073] If different partial areas of the steering wheel rim 4 were determined in both evaluations, method step S5 can be repeated or the method can be terminated without the presence information 26 being provided.

[0074] Fig. 8 shows that after the at least two electrodes 10, 11 have been activated in the second detection mode 16, the at least two electrodes 10, 11 are activated in the measuring mode 17. It can then be checked in a method step S11 whether a result concerning the presence of at least part of the hand 7 in the gripping area of ​​the steering wheel device 2, which result was obtained in the second detection mode 16, matches such a result in the measuring mode 17. If this is the case, result information describing the two results is determined and provided in a method step S12.

[0075] Alternatively or additionally, if the presence of at least part of the hand 7 in the gripping range of the steering wheel device 2 is detected when the at least two electrodes 10, 11 are activated in the measuring mode 17, the at least two electrodes 10, 11 can then be activated in the first detection mode 15 and / or in the second detection mode 16. In method step S11, it is then checked whether the presence of at least part of the hand 7 in the gripping range of the steering wheel device 2 is also detected in the first detection mode 15 or in the second detection mode 16. If this is the case, the result information 27, which describes the results in the measuring mode 17 and in the respective detection mode 15, 16, is determined and provided in method step S12.

[0076] It can therefore be provided that only if the match was determined during the check in method step S11, the result information 27, which describes the presence or absence of at least part of the hand 7 in the gripping area of ​​the steering wheel device 2, is determined and provided. The result information 27 can then be provided by the control device 19 of the steering wheel device 2 for a control unit of the motor vehicle 1. For this purpose, it can be transmitted to the control unit. Overall, the examples show a crosstalk and heating improvement for a hand recognition function with multiple zones, i.e., with multiple electrodes 10, 11.

Claims

Patent claims 1. Method for operating a steering wheel device (2) with a combined heating and detection device (3) which has at least two electrodes (10, 11) which are arranged distributed on a steering wheel rim (4) of the steering wheel device (2), wherein the at least two electrodes (10, 11) are alternately in a heating mode (14) for heating the steering wheel device (2) and in a first detection mode (15) for detecting the presence of at least part of a hand (7) in a gripping area of the steering wheel device (2), characterized in that in the first detection mode (15) a first measured value is recorded (S1) jointly for the at least two electrodes (10, 11) and it is checked (S2) whether the recorded first measured value deviates from a predetermined reference value, wherein only if this is the case the at least two electrodes (10, 11) in a second detection mode (16) for detecting the presence of at least part of the hand (7) in the gripping area of the steering wheel device (2) (S3), in which a respective second measured value is individually recorded and evaluated for each of the at least two electrodes (10, 11).

2. Method according to claim 1, characterized in that by respective evaluation of the respective detected second measured value, that electrode (10, 11) of the at least two electrodes (10, 11) is determined in whose detection range at least the part of the hand (7) is present.

3. Method according to claim 1 or 2, characterized in that the at least two electrodes (10, 11) are controlled again in the heating mode (14) after being controlled in the second detection mode (16) (S4).

4. Method for operating a steering wheel device (2) with a combined heating and detection device (3) which has at least two electrodes (10, 11) which are arranged distributed on a steering wheel rim (4) of the steering wheel device (2), wherein in a measuring mode (17) a measurement is carried out between two electrodes (10, 11) of the at least two electrodes (10, 11) in order to detect the presence at least part of a hand (7) in a gripping area of the steering wheel device (2), characterized in that during this measurement a first electrode (10) of the two electrodes (10, 11) is controlled to heat the steering wheel device (2).

5. The method according to claim 4, characterized in that as a measurement between the two electrodes (10, 11), the first electrode (10) is operated in an excitation mode in which a temporal variation of an electrical charge of the first electrode (10) is predetermined, and a second electrode (11) of the two electrodes (10, 11) is operated in a reception mode in which capacitive measurement information describing the second electrode (11) can be detected, wherein the detected capacitive measurement information is influenced at least by the temporal variation of the electrical charge of the first electrode (10), so that by evaluating the detected capacitive measurement information the presence of at least part of the hand (7) can be detected.

6. Method according to claim 5, characterized in that a mode of the respective electrode (10, 11) is continuously changed between the excitation mode and the reception mode, wherein only the respective electrode (10, 11) which is operated in the excitation mode is always controlled for heating the steering wheel device (2).

7. Method according to one of claims 4 to 6, characterized in that the first electrode (10) experiences a voltage change and a voltage drop or voltage value is specified via the first electrode (10), so that if at least part of the hand (7) is present in the gripping area of the steering wheel device (2) during the voltage change, a measured value of the measurement between the two electrodes (10, 11) depends on the partial area of the steering wheel rim (4) in which at least part of the hand (7) is present, wherein the presence of at least part of the hand (7) is detected in a spatially resolved manner by evaluating the measured value.

8. Method according to claim 7, characterized in that the spatially resolved determination is checked by the first electrode (10) again undergoes a voltage change, a reverse voltage drop, in particular a charge change in the opposite direction, is specified via the first electrode (10) than before and the evaluation of the measured value is repeated, wherein only if the same partial area of the steering wheel rim (4) is determined in both evaluations (S9), presence information (26) describing this partial area is provided (S10).

9. Method according to one of claims 1 to 3 and one of claims 4 to 8, characterized in that after the at least two electrodes (10, 11) have been activated in the second detection mode (16), the at least two electrodes (10, 11) are activated in the measuring mode (17) and it is checked whether a result concerning the presence of at least part of the hand (7) in the gripping area of the steering wheel device (2), which result was obtained in the second detection mode (16), corresponds to such a result in the measuring mode (17).

10. Method according to one of claims 1 to 3 and one of claims 4 to 8, characterized in that if the presence of at least part of the hand (7) in the gripping area of the steering wheel device (2) is detected when the at least two electrodes (10, 11) are activated in the measuring mode (17), the at least two electrodes (10, 11) are then activated in the first detection mode (15) and / or in the second detection mode (16) and a check is carried out to determine whether the presence of at least part of the hand (7) in the gripping area of the steering wheel device (2) is now also detected.

11. Method according to claim 9 or 10, characterized in that only if a match was determined during the checking (S11), result information (27) describing the presence or absence of at least part of the hand (7) in the gripping area of the steering wheel device (2) is determined and provided (S12), in particular by means of a control device (19) of the steering wheel device (2).

12. Combined heating and detection device (3) for a steering wheel device (2) for a motor vehicle (1), wherein the heating and detection device (3) has at least two electrodes (10, 11) and is designed to operate the at least two electrodes (10, 11) alternately in a heating mode (14) for heating the Steering wheel device (2) and, in a first detection mode (15), to detect the presence of at least part of a hand (7) in a gripping range of the steering wheel device (2), characterized in that the heating and detection device (3) is designed to detect a first measured value jointly for the at least two electrodes (10, 11) in the first detection mode (15), to check whether the detected first measured value deviates from a predetermined reference value, and only if this is the case, to control the at least two electrodes (10, 11) in a second detection mode (16) to detect the presence of at least part of the hand (7) in the gripping range of the steering wheel device (2), in which a respective second measured value is detected and evaluated individually for each of the at least two electrodes (10, 11).

13. Combined heating and detection device (3) for a steering wheel device (2) for a motor vehicle (1), wherein the heating and detection device (3) has at least two electrodes (10, 11) and is designed to carry out a measurement between two electrodes (10, 11) of the at least two electrodes (10, 11) in a measuring mode (17) in order to detect the presence of at least part of a hand (7) in a gripping area of the steering wheel device (2), characterized in that the heating and detection device (3) is designed to control a first electrode (10, 11) of the two electrodes (10, 11) for heating the steering wheel device (2) during this measurement.

14. Steering wheel device (2) for a motor vehicle (1) with a combined heating and detection device (3) according to claim 12 or 13, wherein the at least two electrodes (10, 11) of the heating and detection device (3) are arranged distributed on a steering wheel rim (4) of the steering wheel device (2).

15. Motor vehicle (1) with a steering wheel device (2) according to claim 14.

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